The invention relates to a method for production of polyurethane foams and of foamed, thermoplastic synthetic resins, to new blowing agents suitable for this purpose as well as to polyurethane foam and to foamed synthetic resins, which can be obtained using the blowing agents.
Polyurethane foams are used as thermally insulating and noise-insulating building materials. The production of one-component and multi-component polyurethane foams with blowing agents based on liquefied carbon dioxide is disclosed in the WO 96/14354.
Foamed, thermoplastic synthetic resins can be used, for example, in the form of panels, as thermally insulating and noise-insulating building materials. U.S. Pat. No. 5,276,063 discloses a method for producing extruded, closed-cell alkenylaromatic polymers using a blowing agent mixture, which contains 1,1-difluoroethane as well as a further blowing agent with a lower vapor pressure and an even higher solubility in the molten polymer. Suitable alkenylaromatic polymers are, for example, polymers of styrene, xcex1-methylstyrene, ethylstyrene, vinylbenzene, vinyltoluene, chlorostyrene and bromostyrene. These polymers can, if desired, contain copolymers, such as acrylic acid, acrylonitrile or butadiene. U.S. Pat. No. 5,204,169 discloses the production of foamed, thermoplastic polymers, such as polystyrene, using perfluorinated hydrocarbons with two carbon atoms. The foamed material is suitable particularly for food packaging. The EP-A-0 436 847 discloses the production of foamed thermoplastic molded objects based on polyphenylene ether resins. Hydrocarbons are recommended as blowing agents. Halogenated hydrocarbons with one or two carbon atoms are also mentioned as being usable.
It is an object of the present invention to provide a method for the production of polyurethane foams by means of a selected, novel advantageous blowing agent. This objective is accomplished by the method and the blowing agents of the present invention.
It is an object of the present invention to provide a method for the production of foamed, thermoplastic synthetic resins by means of a novel, advantageous blowing agent. This objective is accomplished by the method and the blowing agents of the present invention.
The starting point was the surprising realization that pentafluorobutane, particularly 1,1,1,3,3-pentafluorobutane (HFC-365mfc), in admixture with certain other blowing agents, is a very suitable composition for the production of polyurethane foams or of thermoplastic synthetic resin foams.
According to the inventive method for producing polyurethane foams and of foamed thermoplastic resins by foaming a thermoplastic synthetic resin with the help of a blowing agent, a composition is used as blowing agent, which contains or consists of a) pentafluorobutane, preferably 1,1,1,3,3-pentafluorobutane (HFC-365mfc) and b) at least one further blowing agent selected from the group comprising low-boiling, optionally halogenated hydrocarbons, ethers and halogenated ethers; difluoromethane (HFC-32); difluoroethane, preferably 1,1-difluoroethane (HFC-152a); 1,1,2,2-tetrafluoroethane (HFC-134); 1,1,1,2-tetrafluoroethane (HFC-134a); pentafluoropropane, preferably 1,1,1,3,3-pentafluoropropane (HFC-245fa); hexafluoropropane, preferably 1,1,2,3,3,3-hexafluoropropane (HFC-236ea) or 1,1,1,3,3,3-hexafluoropropane (HFC-236fa); and heptafluoropropane, preferably 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea).
The preferred pentafluorobutane is HFC-365mfc. This is explained in greater detail in the following.
According to one embodiment, a blowing agent is used, which consists of 1,1,1,3,3-pentafluorobutane, 1,1,1,3,3-pentafluoropropane and at least one of the blowing agents named under b).
The preferred embodiment contains 1,1,1,3,3-pentafluorobutane as the component named under a).
The inventive method provides that a composition is used as blowing agent, which contains or consists of 1,1,1,3,3-pentafluorobutane (HFC-365mfc) and at least one further blowing agent selected from the group consisting low-boiling, optionally halogenated hydrocarbons, ethers and halogenated ethers; difluoromethane (HFC-32); difluoroethane, preferably 1,1-difluoroethane (HFC-152a); 1,1,2,2-tetrafluoroethane (HFC-134); 1,1,1,2-tetrafluoroethane (HFC-134a); pentafluoropropane, preferably 1,1,1,3,3-pentafluoropropane (HFC-245fa); hexafluoropropane, preferably 1,1,2,3,3,3-hexafluoropropane (HFC-236ea) or 1,1,1,3,3,3-hexafluoropropane (HFC-236fa); and heptafluoropropane, preferably 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea).
The concept of xe2x80x9clow-boiling, optionally halogenated hydrocarbons, ethers and halogenated ethersxe2x80x9d means compounds with a boiling point lower than 70xc2x0 C., preferably lower than 55xc2x0 C. Suitable hydrocarbons are especially those with two to five carbon atoms, for example, ethane, propane, butane, pentane, cyclopentane and hexane, as well as mixtures thereof. Moreover, isomerically pure compounds or mixtures of different isomers can be used. xe2x80x9cButanexe2x80x9d is understood to be mixtures of n-butane and i-butane. Such mixtures are commercially available. Pure n-butane or i-butane or their mixtures of any composition can also be used, but are very expensive. The same holds true for higher homologs, such as pentane, etc. CH2Cl2, for example, is a usable halogenated hydrocarbon.
Preferably, the blowing agent composition contains 5 to 95% by weight of 1,1,1,3,3-pentafluorobutane and especially 10 to 70% by weight.
Blowing agent compositions which, in addition to HFC-365mfc and one or several of the fluorinated hydrocarbons or hydrocarbons given above, also contain liquefied carbon dioxide, are likewise well suited for use in the inventive method. In that case, preferably 2 to 50% by weight of carbon dioxide are contained in the blowing agent composition. In addition, the blowing agent composition may contain up to 30% by weight of additives, which modify the properties of the synthetic resin that is to be produced.
Particularly suitable blowing agents include, for example, the following compositions, which may contain or consist of (examples of compositions, the parts by weight being given in parentheses):
HFC-365mfc and HFC-152a (70:30);
HFC-365mfc and HFC-32 (70:30); 
HFC-365mfc, HFC-152a and CO2 (60:30:10);
HFC-365mfc, HFC-32 and CO2 (60:30:10);
HFC-365mfc, HFC-152a and butane (60:30:10);
HFC-365mfc, HFC-32 and butane (60:30:10);
HFC-365mfc, HFC-152a and HFC-134a (60:25:15);
HFC-365mfc, HFC-32 and HFC-134a (60:25:15);
HFC-365mfc and dimethyl ether (80:20);
HFC-365mfc and pentane (50:50);
HFC-365mfc and propane (70:30);
HFC-365mfc and ethane (90:10);
HFC-365mfc, pentane and CO2 (45:45:10);
HFC-365mfc, butane and CO2 (50:40:10);
HFC-365mfc, propane and CO2 (70:20:10);
HFC-365mfc, ethane and CO2 (90:5:5).
Preferred blowing agent compositions contain 1,1,1,3,3-pentafluorobutane and/or difluoromethane and 1,1,-difluoroethane or they consist of these compounds. In particular, compositions are used, which contain or consist of 10 to 70% by weight of HFC-365mfc and 90 to 30% by weight of HFC-152a and/or HFC-32.
A preferred embodiment, the preparation of polyurethane (PU) foams, is explained in detail.
The outstandingly useful flame retardants include, for example reactive flame retardants, such as brominated polyols. Flame retardants, based on organic phosphorus compounds, such as phosphate esters and phosphonates, are likewise suitable. These have organic groups, which may be substituted by one or more halogen atoms. The organic groups have an aliphatic or aromatic character. Very well suitable are phosphate esters and phosphonate esters, which are substituted by three C1 to C6 alkyl groups, which may have one or two halogen atoms, such as trischloroisopropyl phosphate, trischloroethyl phosphate, trischloropropyl phosphate, dimethylethyl phosphate, trisdichloroisopropyl phosphate, dimethylmethyl phosphonate; trischloropropyl phosphate is preferred.
One embodiment of the inventive method of producing polyurethane foams provides that if a) is HFC-365mfc and b) 1,1,1,2-tetrafluoroethane (HFC 134a); 1,1,1,3,3-pentafluoropropane (HFC-245fa), 1,1,1,3,3,3-hexafluoropropane (HFC-236fa); or 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), and carbon dioxide, low-boiling optionally halogenated hydrocarbons, ethers or halogenated ethers are not contained, the blowing agent composition contains or consists of less than 50% by weight of 1,1,1,3,3-pentafluorobutane and more than 50% by weight 1,1,1,2-tetrafluoroethane; 1,1,1,3,3-pentafluoropropane; 1,1,1,3,3,3-hexafluoropropane or 1,1,1,2,3,3,3-heptafluoropropane.
The effective amount of blowing agent composition, which is used in the inventive method, can be determined by simple small-scale tests. Advantageously, the blowing agent composition is used in an amount of 1 to 50% by weight, based on the total mixture of the synthetic resin or the preliminary products (polyol, isocyanate, auxiliary materials and blowing agent composition), which is to be foamed.
A further object of the invention are essentially closed-cell polyurethane foams, which are characterized by containing a blowing agent composition, which is to be used in the inventive method, in the cells.
Pursuant to the invention, high-resistance foam and also highly resilient foams, based on isocyanate, can be produced. The production of such foams and the basic materials, which can be used for this purpose, and the nature of the foam production are disclosed in the European patent application EP-A-0 381 986, in xe2x80x9cUllmann""s Encyclopedia of Industrial Chemistryxe2x80x9d, 5th edition, volume A21, pages 665-680, the international patent applications WO 92/00345, 96/30439, 96/14354 and the German Offenlegungsschrift DE 44 22 714 A1. Polyisocyanates with, for example, 2 to 4 isocyanate groups are used.
They have an aliphatic hydrocarbon group with up to 18 carbon atoms, a cycloaliphatic hydrocarbon group with up to 15 carbon atoms, an aromatic hydrocarbon group with 6 to 15 carbon atoms or an aliphatic hydrocarbon group with 8 to 15 carbon atoms. Starting materials, which are particularly preferred in industry are, for example, 2,4- and 2,6-toluylene diisocyanate, diphenylmethane diisocyanate, polymethylenepolyphenol isocyanate and their mixtures. So-called xe2x80x9cmodified polyisocyanatesxe2x80x9d, which contain carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups, can also be used.
Further starting components include compounds with at least two hydrogen atoms capable of reacting with isocyanate groups. These are, in particular, compounds with a molecular weight of 400 to 10,000, which preferably may contain 2 to 8 hydroxyl groups and, furthermore, amino groups, thiol groups or carboxyl groups.
Optionally, further auxiliary materials and additives can be used. For example, chemical blowing agents, such as water or other readily volatile organic substances can be used additionally as physical blowing agents. Catalysts, for example, tertiary amines such as dimethylcyclohexylamine and/or organometallic compounds, such as tin salts of carboxylic acids, can also be used. Surface active additives, such as emulsifiers or foam stabilizers, such as siloxane polyether copolymers, can be used, as can reaction retarding agents, cell regulators, such as paraffins, fatty alcohols or dimethylpolysiloxanes, pigments, dyes, flame retardants, such as phosphate esters or phosphonate esters, for example, trischloroisopropyl phosphate, can be used. Furthermore, stabilizers, which prevent aging and weathering effects, plasticizers, fillers, dyes, antistatic agents, nucleating agents, pore regulators or biocides can be used.
Suitable catalysts are named, for example, in the international patent application WO 96/14354. These include organic amines, amnine alcohols and aminoethers, for example, morphiline compounds, such as dimethylcyclohexylamine, diethanolamine, 2-dimethylaminoethyl-3-dimethylaminopropyl ether, 2-dimethylaminoethyl ether, 2,2-dimorpholinodiethyl ether, N,N-dimethylaminoethylmorpholine and N-dimethylmorpholine. Organometallic compounds, such as tin, cobalt or iron compounds, can also be used as catalyst. Examples are tin dioctoate, cobalt naphthenate, dibutyl tin dilaurate and iron acetonyl acetate.
The blowing agents may contain auxiliary materials and additives, one or more catalysts, flame retardants, emulsifiers, foam stabilizers, binding agents, cross linking agents, UV stabilizers, nucleating agents and optionally further blowing gases. The blowing agent may be added, for example, to the propolymers of polyol and polyisocyanate or diisocyanate, which are then foamed.
It is an advantageous feature of the inventive method that the blowing agent composition employed, which also is a part of the invention, has advantageous properties with respect to ODP, GWP and photosmog. Compared to polyurethane foams, which have been produced with pure hydrocarbons as blowing agents, the foams, produced by the inventive method, are distinguished by a better thermal conductivity.
A particular advantage of the polyurethane foams, obtainable by the inventive method, becomes effective at lower temperatures, generally below about 15 C. Surprisingly, the polyurethane foams, which can be obtained by the inventive method, not only have a more advantageous thermal conductivity (that is, less heat is transferred) than foams, which were prepared from pure hydrocarbons, but even compared to foams, which were prepared with pure pentafluorobutane (HFC-365mfc), the thermal conductivity is lower. In largely close-celled polyurethane foams, which were produced with blowing agent mixtures, which contain pentafluorobutane, preferably 1,1,1,3,3-pentafluorobutane, and at least one of the above-named further blowing agents, a synergistic effect of the blowing agent mixtures used can be noted with respect to the thermal conductivity, that is, the heat insulation capability. The polyurethane foams, obtainable using pentafluorobutane, preferably HFC-365mfc and at least one other of the blowing agents named above, are therefore particularly suitable for insulating against cold in a temperature range below about 15xc2x0 C.
In the following, the preparation of thermoplastic foams is explained in detail.
With the inventive method, the thermoplastic synthetic resins, based on polymeric alkenylaromatic compounds and mentioned in U.S. Pat. Nos. 5,204,169 and 5,276,063, and the thermoplastic synthetic resins, based on polyphenyl ether compounds and named in the EP-A-0 436 847 can, for example, be foamed. Thermoplastic synthetic resins based on polyethylene, polyvinylchloride (PVC) and poly(ethylene terephthalate) (PET) and polypropylene can also be foamed. The use of thermoplastic synthetic resins, based on polystyrene, polyethylene and polypropylene, which are to be foamed by the inventive method, is particularly preferred, the use of polystyrene as thermoplastic synthetic resin being especially preferred.
One embodiment of the inventive method of producing synthetic resins on the basis of polystyrene or polyethylene provides that if a) is HFC-365mfc and b) 1,1,1,2-tetrafluoroethane (HFC 134a); 1,1,1,3,3-pentafluoropropane (HFC-245fa), 1,1,1,3,3,3-hexafluoropropane (HFC-236fa); or 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), but carbon dioxide is not contained, the blowing agent composition contains less than 50% by weight of 1,1,1,3,3-pentafluorobutane and more than 50% by weight 1,1,1,2-tetrafluoroethane; 1,1,1,3,3-pentafluoropropane; 1,1,1,3,3,3-hexafluoropropane or 1,1,1,2,3,3,3-heptafluoropropane or consists thereof. The same proviso also holds good for this embodiment, if no other blowing agent from the group of low-boiling, optionally halogenated hydrocarbons, chlorine and halogenated ethers is contained.
Advantageously, the blowing agent composition is used in an amount of 1 to 30% by weight, based on the total mixture of the thermoplastic synthetic resin and blowing agent composition, which is to be foamed.
A further object of the present invention is a blowing agent composition, which can be used for the inventive method. It contains or consists of a) pentafluorobutane, preferably 1,1,1,3,3-pentafluorobutane (HFC-365mfc) and b) at least one further blowing agent selected from the group comprising low-boiling, optionally halogenated hydrocarbons, ethers and halogenated ethers; difluoromethane (HFC-32); difluoroethane, preferably difluoroethane (HFC-152a); 1,1,2,2-tetrafluoroethane (HFC-134); 1,1,1,2-tetrafluoroethane (HFC-134a); pentafluoropropane, preferably 1,1,1,3,3-pentafluoropropane (HFC-245fa); hexafluoropropane, preferably 1,1,2,3,3,3-hexafluoropropane (HFC-236ea) or 1,1,1,3,3,3-hexafluoropropane (HFC-236fa); and heptafluoropropane, preferably 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea). A preferred composition contains or consists of a) 1,1,1,3,3-pentafluorobutane (HFC-365mfc) and b) at least one further blowing agent selected from the group comprising ethane, propane, butane, pentane; difluoromethane (HFC-32); difluoroethane (HFC-152a); 1,1,2,2-tetrafluoroethane (HFC-134); 1,1,1,2-tetrafluoroethane (HFC-134a); 1,1,1,3,3-pentafluoropropane (HFC-245fa); 1,1,1,3,3,3-hexafluoropropane (HFC-236fa) and 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea). Preferably it contains 5 to 95% by weight and, especially, 10 to 70% by weight of 1,1,1,3,3-pentafluorobutane (HFC-365mfc).
Suitable compositions contain or consist of HFC-365mfc and HFC-152a; HFC-365mfc and HFC-32; HFC-365mfc, HFC-152a and CO2; HFC-365mfc, HFC-32 and CO2; HFC-365mfc, HFC-152a and butane; HFC-365mfc, HFC-32 and butane; HFC-365mfc, HFC-152a and HFC-134a; HFC-365mfc, HFC-32 and HFC-134a; HFC365mfc and dimethyl ether; HFC-365mfc and pentane; HFC-365mfc and propane; HFC-365mfc and ethane; HFC-365mfc, pentane and CO2; HFC-365mfc, butane and CO2; HFC-365mfc, propane and CO2; HFC-365mfc, ethane and CO2.
According to a preferred embodiment, the blowing agent composition contains 1,1,1,3,3-pentafluorobutane (HFC-365mfc) and difluoromethane and/or 1,1-difluoroethane (HFC-152a) or consists of these compounds. In particular, 10 to 70% by weight of 1,1,1,3,3-pentafluorobutane and 90 to 30% by weight of 1,1-difluoroethane or difluoromethane are contained or the blowing agent composition consists of these components in the quantity ranges given.
The blowing agent composition may also contain 2 to 50% by weight of liquefied carbon dioxide.
One embodiment of the blowing agent composition, provides that if a) HFC-365mfc and b) 1,1,1,2-tetrafluoroethane (HFC-134a); 1,1,1,3,3-pentafluoropropane (HFC-245fa); 1,1,1,3,3,3-hexafluoropropane (HFC-236fa) or 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), but no carbon dioxide are contained, the blowing agent composition contains or consists of less than 50% by weight of 1,1,1,3,3-pentafluorobutane and more than 50% by weight of 1,1,1,2-tetrafluoroethane; 1,1,1,3,3-pentafluoropropane; 1,1,1,3,3,3-hexafluoropropane or 1,1,1,2,3,3,3-heptafluoropropane. The same proviso also applies to this embodiment, provided that no further blowing agent from the group of low-boiling, optionally halogenated hydrocarbons, ethers and halogenated ethers is contained.
A further object of the invention are essentially closed-cell foamed synthetic resins, which are characterized by containing the inventive blowing agent composition in the cells. In particular, it is a question of essentially closed-cell, foamed, thermoplastic synthetic resins, preferably based on polystyrene, polyethylene, polypropylene, PVC or PET and, in particular, of polystyrene.
The thermoplastic foams, which can be obtained with the inventive method, have the advantage that the closed-cell character is better than that obtained when, for example, HFC-134a is used as blowing agent. In the case of polystyrene melt, the processability is noted to be better than when HFC-134a is used by itself. The inventive blowing agents are sufficiently soluble. The inventive blowing agents have no ODP and only a slight GWP. The effect on the formation of photosmog is extremely slight.
Improved properties in relation to thermal conductivity are a particular advantage of the inventive foams. Compared to using only HFC-134a, HFC-152a and HFC-32 as blowing agent, the residual content of blowing agent in the cells of the foam, is higher.